problem with 90 deville

I have aproblem with my 90 deville, it has a missfire and lacks power. I've changed plugs wires etc, changed fuel filter too, not getting any codes. Can anyone help

Misfire when, at idle, need more info here?

it misses at idle and clears at higher speeds. it takes a while to get to speed. The car hesitates when taking off. I was driving up a hill and was losing speed with the pedal all the way to the floor and when I first got the car I took the hill like nothing.

Try and isolate which cylinder has the misfire, if this is port injection disconnect one injector at a time and see if you can feel the cylinder that does not change the idle roughness, then check that plug and or wire. If all ok could be a bad injector, but additional diagnosis must be done.

Thanks for the help will try this